Two-State Spin Systems with Negative Interactions

09/09/2023
by   Yumou Fei, et al.
0

We study the approximability of computing the partition functions of two-state spin systems. The problem is parameterized by a 2× 2 symmetric matrix. Previous results on this problem were restricted either to the case where the matrix has non-negative entries, or to the case where the diagonal entries are equal, i.e. Ising models. In this paper, we study the generalization to arbitrary 2× 2 interaction matrices with real entries. We show that in some regions of the parameter space, it's #P-hard to even determine the sign of the partition function, while in other regions there are fully polynomial approximation schemes for the partition function. Our results reveal several new computational phase transitions.

READ FULL TEXT

Please sign up or login with your details

Forgot password? Click here to reset